1. Technical Field
This invention is related to a fuel vapor separator used in fuel delivery systems of a marine engine for recovery of fuel vapors and to prevent fuel spills when the engine is tilted.
2. Discussion
Small outboard marine engines are usually detachable and mounted to the transom of a boat. These engines typically include an integrated fuel system which draws liquid fuel under suction from a can or tank in the boat. The fuel is routed through a vapor separator unit to condense or recover vapors to be burned by the engine through the air intake system. The fuel in the vapor separator is delivered at high pressure to the fuel injection system. Larger inboard or inboard/outboard marine engines also typically include an integrated fuel system which draws fuel from under suction and is routed through a vapor separator unit to capture and combust the captured vapors by the engine to prevent fuel vapor build-up in enclosed areas of the boat.
The marine industry has long recognized that fuel vapors on boats are an issue, particularly in enclosed compartments. To prevent fuel spills, boat safety regulations have long required that fuel routed between a tank and engine be sucked under a vacuum instead of being provided at pressure, as is commonly performed in the automobile industry. Therefore, fuel is withdrawn from the tank at a negative pressure to prevent fuel spilling into the boat, should the fuel line rupture. However, at low pressures, fuel readily vaporizes, especially when combined with high temperatures near engines and jarring conditions as a boat passes over waves. Beyond capturing vapors to prevent emissions or to prevent the potential for uncontrolled combustion of vapors near an engine, if vapors are in the fuel provided to the engine, a condition known as vapor lock may occur.
Vapor separators are designed to address the above vapor issues. Some vapor separators allow heated fuel from the fuel rail of the fuel injectors to be returned and any vapors present in the fuel rail to be condensed back into a liquid before the fuel is reintroduced to the high pressure pump and provided to the fuel rail of the injector system. In some outboard motors, the vapors may be vented to the atmosphere by the vapor separator however in engines that are enclosed in compartments, the fuel vapor is provided to the engine fuel intake system through a vacuum line connection and combusted in a controlled manner within the engine.
Vapor separators include a vapor vent valve in most marine applications with a float actuated valve for automatically closing the vent line whenever the fuel level in the separator rises above a predetermined level. This float valve prevents liquid fluid from being provided into the air intake of the engine through the vacuum line designed to provide only fuel vapors to the engine. Additionally, the float mechanism is also designed to close the vent line, in particular for removable outboard motors, when the engine is tipped so that liquid fuel does not drain out of the vapor vent.
Prior art fuel vapor vent valve arrangements are commonly a buoyant float supported by the liquid fuel just below the vapor line connected to a needle valve which closes when the liquid fuel lifts the float. A typical prior art needle vent valve system 200 is depicted in FIG. 1. These needle valves 200 include floats 202 commonly carried on a pivot pin 204, with the rotational axis of the float pivot being oriented parallel relative to the pivotal axis of the engine mounting bracket so that the float will close the vent passage 206 with a needle valve 208 whenever the engine is rotated to a tilt condition such as an in an outboard motor with the prop out of the water. Closing the passage when the engine is tilted prevents the liquid fuel from running through the vapor separator when the engine is shut off and tilted or prevents liquid fuel from running through the vapor portion of the vapor vent valve to the air intake of the engine while it is running.
Many outboard marine engines are often configured to be manually removed from the boat after the use and stored. When the engine is removed, users commonly lay the engine on its side to protect the prop and tiller arm when placing the engine on a trailer, in a vehicle cargo area, or perhaps on the bed of a pick-up truck. When the marine engine is laid on its side, the pivotal axis of the vent valve mechanism is no longer aligned with the engine and many times the float valve will not properly close the needle valve or the needle valve later becomes displaced during transit which may allow liquid fuel to leak through the vapor exit on the vapor separator to the engine, engine compartment, or area within the engine is stored. Accordingly, an improved fuel vapor separator in which the vent control device can accommodate engine tipping in non-conventional directions is desirable. It is also desirable to have a vapor separator that does not allow solid fuel to vent through the vapor outlet during engine operation due to vibrations or jarring, such as wavy conditions where the valve or float is moved, even though liquid fuel is present, thereby allowing liquid fuel to splash into the vapor outlet. Any splashing of liquid fuel into the vapor outlet causes, in systems where the vapor outlet is connected to the air intake allows liquid fuel to be provided to the air intake of the engine causing a condition of too much fuel, commonly resulting in stalling of the engine. Therefore, it is desirable to prevent instantaneous venting due to vibration and allow for control of when the vapor is vented through the vapor separator.
Vapor separators are not used in automotive applications because the factors which produce excessive vapors in marine applications are generally not present. Furthermore, vehicles have typically less concern regarding fuel vapor build-up in enclosed areas of the vehicle. Some automotive emission systems incorporate a “roll-over” vent valve into the fuel tank, however these are passive features in the emission system that simply protect the open vent line to a vapor collection canister. The automotive engine would continue to operate unaffected and without interruption if the roll-over vent valve was disabled or removed. In comparison, in marine systems where the vapor vent valve is an active component of the engine, any failure or malfunction potentially would disable the engine entirely.